This invention relates generally to magnetic resonance imaging (MRI), and more particularly the invention relates to MRI with parallel imaging.
Magnetic resonance imaging (MRI) is a non-destructive method for the analysis of materials and is an approach to medical imaging. It is generally non-invasive and does not involve ionizing radiation. In very general terms, nuclear magnetic moments are excited at specific spin precession frequencies which are proportional to the local magnetic field. The radio-frequency signals resulting from the precession of these spins are received using pickup coils. By manipulating the magnetic fields, an array of signals is provided representing different regions of the volume. These are combined to produce a volumetric image of the nuclear spin density of the body.
Magnetic resonance (MR) imaging is based on nuclear spins, which can be viewed as vectors in a three-dimensional space. During an MRI experiment, each nuclear spin responds to four different effects: precession about the main magnetic field, nutation about an axis perpendicular to the main field, and both transverse and longitudinal relaxation. In steady-state MRI experiments, a combination of these effects occurs periodically.
Magnetic Resonance Imaging (MRI) has been very successful in imaging parts of the body that are easily immobilized, such as the brain and joints. Its success has been much more limited for rapidly changing settings, as in imaging the heart and dynamic imaging. MRI requires a relatively long scan time compared to other imaging modalities. This requirement limits and sometimes prevents its use in important applications.
MRI data are collected in the spatial frequency domain (k-space). In most imaging scenarios, scan time is directly related to the number of data samples needed for proper reconstruction. Typically, the k-space sampling density is set by the Nyquist criterion based on the image resolution and field of view (FOV).
US Patent Application 2006/0029279 to Donoho, published on Feb. 9, 2006, entitled “Method and Apparatus For Compressed Sensing,” which is incorporated by reference for all purposes, provides a method of approximating a digital signal or image using compressed sensing. US Patent Application 2006/0239336 to Baraniuk et al., published Oct. 26, 2006, entitled “Method and Apparatus For Compressive Imaging Device,” which is incorporated by reference for all purposes, provides a method for acquiring an image or video sequence from incoherent projections.